This study is designed to show a relationship between local anesthetic induced convulsions and changes in brain amines, i.e., serotonin, norepinephrine, and dopamine. Approximately 1120 male Sprague-Dawley rats will be used and only rat brain regions will be analyzed (when appropriate) for the three amines. Brain regions to be analyzed consist of the cerebral cortex, striatum, midbrain, hypothalamus, cerebellum, and pons-medulla oblongata. A total of fourteen experiments are planned and consist of: 1) Dose-response curves with lidocaine challenge and manipulation of brain serotonin; 2) Dose-response curves with lidocaine challenge and manipulation of brain norepinephrine and dopamine; 3) Time-course measurement of steady-state levels of the three amines in brain regions with lidocaine challenge; 4) Synthesis rate of serotonin in brain regions with tranylcypromine alone and with lidocaine; 5) Synthesis rate of serotonin in brain regions with probenecid alone and with lidocaine; 6) Time-course depletion of norepinephrine and dopamine in brain regions by alpha-methyl-p-tyrosine alone and with lidocaine; (7) Time-course depletion of norepinephrine in brain regions by FLA-63 alone and with lidocaine; 8) Repeat of the seven experiments with the drug procaine instead of lidocaine. The over-all objective is to characterize the mechanism of induction of local seizures at the level of a brain pathway in a particular region of rat brain.